Sound receiver



April 22, 1930. I H. c. HAYES SOUND RECEIVER 2 Sheets-Sheet 1 Filed Aug. 17, 1927 Snow 1 60a Ham s y C.

A qy s 33 1;; G bio 044mg umewpml April 22, 1930. c HAYES 1,755,583

SOUND RECEIVER Filed Aug. 17, 1927 2 Sheets-Sheet 2 HH HIHH avwemtoz War/g Haye Patented Apr. 22, 1930' PATENT OFFICE f HARVEY c. .HAYES, or wasnnie'roiv, DISTRICT or oorumnm.

soum) aEcEIvEa Application filed August 17, 1927. smart. 213,632.

- (GRANTED mums. THE ACT or MARCH 3, 1883, as aianuntii mu. 30.1928; 370 o. e. 757) 3' This invention relates primarily to im provements in devices for convertingsound or similar waves intoelectrical effects. More particularly it is the purpose of the invention 5 to provide an improved form of magnetoelect-ric device of the type commonly termed a magnetophone for transforming a mechanical impulse into an electric current or change in an already existing current.

to employ devices of the micro hone type for the purpose of detecting soun s, particularly where the impulses are relatively feeble. Devices of this character are more sensitive than other devices which might be employed but they are not uniform or reliable in their action. When it is desired to match receivers, as required -for binaural reception, it is impractical to employ microphones since even if once matched they will not remain in this condition for any length of time.

The present invention contemplates a form of magnetophone which is accurate and re- .liable in its action and which'is of sufficient sensitivity to adapt it for the reception of relatively feeble sound or similar waves.

An importantconsideration in the development of the present novel devices was the need for eliminating as far as possible the usual restoring forces acting upon themmature or other movable part of a magnetoelectric device tending to prevent its displacemerit It will be apparent that when the restoring forces are relatively large the sensitivity of the instrument is necessarilylow.

' By the present invention the restoring forces tendlng to oppose the displacement of certain of the parts under'the influence of'a sound receivingdiaphragm are minimized by creating opposition between two substantially equal forces. There is a slight difference in the opposing forces when the balance is upset and this is sufiicient to normally maintain the parts in a central position of equilibrium.

e armature is quite low and may be kept below the spectrum of sound waves which it is desired. to detect. The device is adjustable so that any degree of sensitivity within acer- Heretofore it has been the common practice hence cheap to manufacture.

Due to the relatively small restoring forcesemriioyed the natural or resonant frequency of t . that the intensity and phase relations of the effects upon a sound receiver'change ve'ry rapidly with the frequency when approaching the resonant frequency.

' With the foregoing considerations in view it has been a primary object of the present invention to construct the device with as few parts as possible. All of the parts that are required, furthermore, are simple in form and he assembly is such that the device is compact and rugged and presents very little danger of getting out of order.

Another prominent feature of the present invention is the means adopted for supporting the armature which is vibrated by the sound or similar waves to induce corresponding electrical effects. It is important for the sake of accurate reproduction to so support the armature as to avoid any wobbling motion with respect to the field. Obviously any uncertainty or irregularity in the character of movement of the armature will produce like effects in the induced electric currents which will therefore result in a distorted record or indication. The present invention not only obviates this commoncause of distorted reproduction but also combines in the single means for producing this result the function of restoring the armature to its central position of equilibrium.

Other objects and advantages to be derived from the present invention will be apparent from the detailed description which follows and which will begiven in connection with the accompanying drawings in which:

Figure 1 is a planview' of the assembly constituting one form of the invention." Figure 2 is a cross sectional view along a diameter lin'e'of Figure 1.

aFigure 3 is a view similar to Figure 2 but I I and Figure 4 is a similar view showing a further modification of the invention.

Referring now to Figure 2, there is provided a casing 1 formed of any suitable material, preferably a non-conductor of either magnetic lines of force or electrical current, as, for example, bakelite. A flange 2, formed at one end of the casing is adapted to retain certain of the parts in their proper positions while an annular cap 3, which is screw threaded to the casing at'its other end, serves to aid in retaining the parts as desired. In the space between the flange 2 and the cap 3 there is provided a series of elements including a diaphragm 4 resting against the flange 2. This diaphragm is formed of good magnetic material, such as laminations of transformer steel. 'Adjacent the diaphragm there is a thin annular element 5 also formed of magnetic material and adjacent. this element is a thicker annular steel ring 6; the latter, however, is not of as great a width in the radial direction as the element 5. Annular mem -bers 7, 8, 9, 10 and 11, as well as a-diaphragm 12, serve to fill the remaining space between the flange 2 and the cap 3. Of these the members 7, 9 and 11 are substantially like the element 5, while members Sand 10 are substantially like the heavier annular ring 6. The diaphragm 12 is substantially the same as diaphragm 4 and is preferably made of la m inations of transformer steel. Between the members 5 and 7, and directly inside of the ring 6,'there is mounted a coil 13, while a corresponding coil 14 is similarly mounted within the ring 10. An armature comprising a member having a knurled head 15 and a shank 16, adapted to support small collars 17' and 18% well as a disc 19, is mounted between and supported by the diaphragms 4 and 12. It will be apparent that this mode of mounting. the armature will serve to permit the desired steady axial movement of the latter and will eliminate the objectionable wobbling. which would result in distorted reproduction. A nut 20 is provided on the outside of the diaphragm 4 and this nut cooperates with threads at one end of the shank 16 to hold the parts comprising the armature together. All of the parts of the armature may be formed-of magnetic material, if desired, but it is essential only that the annular members 17 and 18, as

well as the disc 19, be formed of such material, as, for example,steel.

One of he terminals of each'of the coils 13 and 14 is connect d to one terminal, such 21. The remaining terminal of each of the coils is con nected to one end of. a primary coil of a transformer. Thus the coil 13 may be. 0011-.

. necfied to the rimary winding 22, while the coil 14 may connected to the primary winding 23. The opposite ends of the wind- One of these fields will-tend to draw themmature in the direction of the diaphragm 4 and the other will tend to dfawthe armature in the direction of the diaphragm 12.

In operation the armature through the knurled head 15 will be connected by any suitable means, such as the screw threaded rod illustrated, to a diaphragm 27 which is adapted to receive the sound or similar waves to be detected. As a sound wave strikes this diaphragm it will first move the armature upwardly in Figure 2, thereby carrying the-disc 19 closer to the member 7 and further away from the member 9. This will decrease the air gap in the upper magnetic circuit which is comprised by the elements 4, 5, 6, 7, 19 and 18, while the lower magnetic circuit, comprised by the elements 9, 10, 11, 12, 17 and 19, will have its air gap between 9 and 19 increased. With the resulting increase and decrease in the reluctance of the lower and upper magnetic circuits, respectively, the flux will be correspondingly decreased and increased, respectively, in these circuits.

.Now by the well known laws of magnetism and electricity the increase in flux in' the upper circuit will tend to induce a current in the coil 13 opposing the increase and therefore will produce a change in the current in the transformer winding 22 in the direction of the arrow indicated. On the other hand, the decrease in the flux through the lower circuit will induce a current tending to bolster up the already existing current in the. coil 14 and transformer winding 23. This change of current, therefore, will be in the direction of the arrow adjacent the winding 23. Va-

riations of the character indicated in the current traversing the windings 22'and 23 will induce corresponding currents in the secondary windings 24 and 25 of the transformers and these. currents under the arrangement illustrated will be combined to add their effects upon a galvanometer 26 in the circuit with them. 7

It will be understood, of course, that the impulses striking the diaphragm 27 will cause alternate up and down movements of the armature'so that the. currents induced in the transformer windings will be alternately firstin the direction indicated and then in the opposite direction.

- In connection with the forces acting upon 7 the armature it is to be noted that the diallO unbalance the magnetic'forces on the arma ture in such a way as to' aid the external impulse. The diflerent-ial between the magnetic forces thus created in the upward direction will in a measure offset the increased restoring forces of the diaphragms 4 and '12 due to their displacement, but the parts will, of course, be so adjustedthat the diaphragms have a slight advantage and will tend to restore the armature to normal. As will be apparent the net restoring force will be relatively small so that the natural frequency of the armature will be below any range of frequencies to be received.

It will be noted that in Figure'2 the source of current 21 is connected in parallel with the two coils 13 and 14'. A series arrangement may be adopted, if desired, but forthis purpose it is necessary to provide a second set of coils in addition to the coils 13 and 14 surrounding the armature. Figure 3 illustrates a suitable arrangement of circuits for this purpose. Coils 13 and 14', corresponding to coils 13 and 14 of Figure 2,-are con nected in series with a D. C. source of electure will vary the flux through the coils 28 and 29, and these may be wound in such relative sense that the currents induced in them will flow in the same direction through the series circuit as, for example, in the direction indicated by the arrow. The combined E. M. F.s induced in the primary windings 30 and 31 of the transformer will induce a corresponding relatively large E. M.'F. in the secondary winding 32 of the transformer and this may be indicated in any suitable way, as by the 'galvanometer- 33. If desired the galvanometer may be placed directly in circuit with the coils 28 and 29 since they carry only induced currents and do not have any constant outside source of current, such asapplied to coils 13 and 14. In the event that the induced currents in themselves are not of suflicient strength toefiect the desired results an amplifier of any suitable construction may be employed. A further modification of the invention is illustrated in Fi ure 4. In this figure the diaphragms 4 an 12 of Figure 2 are replaced by diaphragms' 34 and 35 which are formed of non-magnetic material. The magnetic circuits through the upper and lower coils, therefore, will not include the diaphragms but *each will include a second air gap between annular members 5 and 11 and discs 36 and 39, respectively, carried by the armature. Thus in this modified construction two air gaps are provided in each magnetic circuit, the one at the center ofthe armature being substantially the same as in the nrst embodiment. However, in order to place the vtwo air gaps for each circuit in series, i. e.,

in such relation as to increase or decrease both simultaneously, the armature is provided with two discs 37 and 38 at the center corresponding to disc 19 of Figure 2, while a single stationary member 40 cooperates with these discs in a manner similar to the pair'of elements 7 and 8 of Figure 2. The terminals of the coils in this modified construction may be connected in parallel with a source of current, as illustrated, or, if desired, two sets of coils similar to those shown in Figure 3 may be provided and a series arrangement of circuits may be adopted.

In other respects the device illustratedin Figure 4 is substantialy the same as that illustrated in Figure 2, although this figure illustrates a few of the varied possibilities of changes in construction such as in the form of the closure member for, the casing, here shown-as a screw threadeda'nnular ring 41 I instead of a cap, and in the form of construction of the armature 43 particularly in the purposes without the payment to me of any royalty thereon or therefor.

What I claim is:

-1. In a sound receiver a plurality of coils,

a source of electricity connected with said coils and adapted to produce a plurality of separate magnetic fields around said coils, a rigid, bodily movable armature normally balanced in said magnetic fields, sound responsive means connected with said armature and adapted to reciprocate the latter, resilient members connected with said armature and adapted to restore the latter and means for indicating the changes in flux of the magnetic fields upon movements of the armature.

2. In a sound receiver a plurality of coils adapted to produce magnetic fields, an armature normally balanced in said fields, diaphragms connected to said armature and adapted to restore the same upon displacement, sound responsive means for reciproeating said armature, a magnetic circuit for each of said coils including an annular member, and means carried by said armature in spaced relation with said annular members and adapted to form air gaps therewith in said magnetic circuits, said members and means being relatively movable upon movements of said armature.

3. In a device. for converting mechanical vibrations into electrical energy, a plurality of coils, a plurality, of separate magnetic circuits adapted to carry variable flux through said coils, each circuit being related to a particular coil, said circuits being each provided with an air gap, and means responsive to said mechanical vibrations for increasing the air gap in one of said circuits and simultaneously decreasing the air gap .in another of said circuits.

4. In a device of the class described an fields providing opposed magnetic forces on said armature, elements of magnetic material normally separated by an air gap and relatively movable to vary the air gap upon movement of the armature, said elements being in the circuits of said magnetic fields, and electrical conductors in the fields whose fluxes are thus varied. w

8. In a device of the class described a casing, means within said casing for establishing a plurality of magnetic fields, an armature movable longitudinally in said fields and forming a part of the magnetic circuits, magnetic conductors carried respectively by said armature and said casing adapted to form a plurality or air gaps in each of said circuits, said air gaps in each circuit vbeing arranged in series so as to vary in the same sense upon movements of the armature, and means for detecting the resulting variations in flux through said circuits.

7 HARVEY C. HAYES.

armature, coils surrounding said armature,

means adapted .to establish a plurality oi separate opposed magnetic fields acting on said armature, each of said fields being related to one of said coils, means carried by said armature adapted to vary the flux in said magnetic fields, and means for indicating-the combined variation influx insaid fields.

5.. In a device of the class described a bodily movable armature, diaphragms for supporting the "armature at its ends, means -f0r establishing a plurality of separate magnetic fields providing opposed magnetic 'forces on saidarmature, elements of magnetic material normally separated by an air.

gap and relatively movable to vary the air gap upon movements of the armature, said elements being in the circuits of said magnetic fields, and electrical conductors inthe casing, means within said casing for estabfields whose fluxes are-thus varied, 4

6. In a device of the class described a lishing a plurality of separate magnetic fields, an armature movable longitudinally in said fields and forminga part of the magnetic circuits, magnetic conductors carried respectively. by said armature and saidcasing adapted to form an air gap -in each circuit, and means for detecting the variations in flux through said circ'fiits due to Varying the air gaps upon movements of the armature.

7. In a device of the class describedan armature, diaphragms for supporting the armature at its ends, said diaphragms being i establishing a plurality of separate magnetic formed of non-magnetic material, means for 

